Low Damage Etching of GaN Surfaces via Bias-Assisted Photoenhanced Electrochemical Oxidation in Deionized Water

Properties of GaN surfaces etched by bias-assisted photoenhanced electrochemical (PEC) oxidation in deionized water and subsequent removal of the oxidized material are investigated using Schottky diodes fabricated on etched surfaces. It is demonstrated that with a short anneal at 700 C after removal of the oxide, it is possible to obtain a low damage surface with near ideal breakdown and capacitance-voltage (C-V) characteristics. Good quality Schottky diodes are fabricated on surfaces etched as much as 120 nm. The undercutting of masked surfaces is also demonstrated. Thus, given the band-gap selectivity, the possibility to undercut masked areas, and the low damage surfaces that can be obtained, the process demonstrated in this paper is suitable for use in fabrication of self-aligned GaN bipolar transistor structures.